Musannaf Ibn Abi Shayba 33:55

Affan narrated to us, he said: Mu'awiyah ibn Abd al-Karim narrated to us, from al-Hasan, that the Prophet Dawud (peace be upon him) said: "My God, if every hair of mine had two tongues glorifying You night and day, we would not have fulfilled one of the blessings You have bestowed upon me."